In conventional telecommunications network numbering plans, all symbol strings (e.g., dialed digits) that constitute call-control symbol-sequences (e.g., called numbers) which make up a numbering plan have a direct correspondence to--are unique identifiers of--elements within the telecommunications network. For example, in the North American numbering plan, the called number 0-10288-303-538-4154 consists of the following five symbol strings: "0" identifying a local operator assistance pool, "10288" identifying a particular interexchange carrier, "303" identifying a particular remote geographical area, "538" identifying a particular exchange (i.e., central office), and "4154" identifying a particular port. For another example, the called number 1-303-555-1212 consists of the following three symbol strings: "1" identifying the geographical area exclusive of the local area, "303" identifying a particular remote geographical area, and "555-1212" identifying a particular operator pool. It is apparent from these examples that every entity identified by the symbol strings is a constituent portion of the telecommunications network. It is in this manner that the symbol sequences that are members of conventional network numbering plans serve to specify communications (e.g., call) routes and destinations.
In many situations, the identity of the calling terminal/station may influence or even override the choice of route or destination for the call. For example, individual terminals are assigned a class-of-service, and permissible call routes and permissible destination areas for calls from the terminals are determined by their class of service. Or, all calls to "900" numbers from a particular call-originating station may be blocked. Or, all calls from a particular originating station may be routed to an intercept announcement. Or, in a telemarketing system, a call may be connected to one of a number of destination endpoints (e.g., telemarketing agents' stations) based on the call's Automatic Number Identification (ANI) which identifies the calling terminal. But it will be noted from these examples that the route or destination-influencing information is the identity of the calling terminal, which is--once again--an element of the network.
Of course, the identifying of all of the network elements involved in a call need not be done explicitly by the caller. For example, the network typically obtains the identity of the calling terminal automatically, by determining which port the call is originating at. Also, in some cases, the call-processing intelligence of the network (e.g., the call-processing software of the call-originating switching system in a telephony network) makes default selections of network elements in the absence of them being explicitly specified within a caller-generated call-control sequence. An example thereof is disclosed in U.S. Pat. No. 4,577,066. As disclosed therein, in the absence of a caller dialing an interexchange carrier I.D. as part of the call-originating symbol-sequence, a switching system selects for the call a carrier that is specified in the translations of the calling terminal, or selects a default carrier if no carrier is specified in the translations. However, a carder selection made by the caller by dialing a carrier I.D. overrides a translations-based and a default-based carrier selection.
Many customers of telecommunications systems consider the usual restriction of call-route-and-destination-determinative information to network element-related information to be undesirable and limiting. They wish to extend their ability to influence call-route and destination selection to network-independent criteria.
Examples of the use of information that does not directly identify network elements, to influence call-route or call-destinations selection are rare, however. One related example is the use of authorization or account codes in some telephony systems. When such a system determines that, within a set of possible routes for the call (selected on the conventional basis of identified network elements), none of the call routes authorized to be used by the class-of-service translations of the call-originating terminal are available for use, but that other, expensive but non-authorized, routes do exist within that set of possible routes, it prompts the caller for an authorization or account code that signifies permission to use, and to charge for, one of the non-authorized routes. The call is completed and routed over one of the non-authorized routes only if the caller inputs a valid authorization or account code, and an account associated with the code is billed for the cost of using the route. These codes provide no information on the uses of the calls.
Another example is the use of permissions in some electronic voice-mail systems, as described in U.S. Pat. No. 5,017,917. When a caller accesses such a system and attempts to leave a voice-mail message for a particular called party, the system prompts the caller to input his or her personal I.D. Based on that I.D., the system determines whether the calling person has permission to contact the called person. If so, the system connects the caller to the called party's mailbox; if not, the system connects the caller to an intercept announcement.
A third example is the use of time-of-day routing in some telephony switching systems, such as AT&T private-branch exchanges (PBXs). In these systems, selection of a public-network route for a call is based at least in part on the time of day at which the call is made, either for the purpose of avoiding call-traffic congestion that develops on some routes at certain times of day or for the purpose of selecting the least-expensive route from among routes whose cost varies with the time of day.
The very limited capability to influence call-route and destination selection with network-independent criteria that the art presently provides is inadequate for many customers. For instance, consider a hypothetical example of an attorney in state A having a number of cases pending in a court in state B. The court has separate phone numbers for an internal operator, a civil division, and a criminal division. One of the pending cases is a civil case for client A. Jones who has AT&T as his interexchange carrier. Another two cases are a civil case and a criminal case for client ABC Co. which has a private telecommunications network extending between states A and B. And a fourth case is a criminal case for client B. Doe who has MCI as his interexchange carrier. The attorney herself has AT&T as her personal interexchange carrier. The attorney would like to have the following capability. When she dials one of the courthouse phone numbers, either alone or accompanied by her personal I.D., she wishes to have the call routed to the dialed phone number via AT&T. When she dials one of the courthouse phone numbers accompanied by an account code for ABC Co., she wishes to have the call routed to the dialed phone number via ABC Co.'s private network. When she dials any one of the courthouse phone numbers accompanied by an account code for A. Jones, she wishes to have the call routed to the civil division's phone number via AT&T. And when she dials any one of the courthouse phone numbers accompanied by an account code for B. Doe, she wishes to have the call routed to the criminal division's phone number via MCI.
Capabilities such as the just-presented hypothetical are not available to customers. Prior-art telecommunications networks and their call-processing arrangements and numbering plans are simply not capable of implementing such varied and flexible network-independent call-route-selection and call-destination-selection algorithms.